As shown in FIG. 1, in the third generation mobile communication long term evolution system, a handover method based on the X2 interface of the base station comprises: when the terminal is required to perform handover between the base stations, the source base station to which the terminal belongs selecting a target base station according to a measurement result which is performed by the terminal to the adjacent base stations, and transmitting a handover request message (the message includes information, such as, a source base station identifier, a base station handover type, source cell information and a handover terminal identifier, etc.) to the target base station to request the resource; and the target base station performing the handover admission evolution, allocating the relevant resource (including the access parameter of the handover terminal in the target cell, etc.) for the terminal performing handover to the target base station, and returning a handover request response message to the source base station.
As shown in FIG. 2, in the third generation mobile communication long term evolution system, a handover method based on the S1 interface of the base station comprises: when the terminal is required to perform handover between the base stations, the source base station to which the terminal belongs selecting a target base station according to a measurement result which is performed by the terminal to the adjacent base stations, and the source base station applying for the resource from a single target base station through a mobility management entity (MME), that is, the source base station transmitting the handover request message (the message includes information, such as, a source base station identifier, a base station handover type, source cell information and handover terminal identifier, etc.) to the MME, and then the MME forwarding the handover request message to the target base station; and the target base station performing the handover admission evolution, allocating the relevant resource (including the access parameter of the handover terminal in the target cell, etc.) for the terminal performing handover to the target base station, and returning a handover request response message to the MME, and the MME forwarding the handover request response message to the source base station in the direction of the handover command.
In the above methods that are known in the art, if the evolution result of the target base station is that the handover is unable to be performed, the source base station is required to re-select the target base station and re-transmit the handover request message, which slows the handover of the terminal, increases the handover delay, reduces the handover efficiency, and reduces the key performance indicators (KPI) during the handover.